Sound Characteristics 3 of 3

As we move into the next characteristics of sounds, we will be talking about what happens to sounds to make them unique and interesting.  When we keep all of these topics in mind, it will help us be better sound engineers. The last two elements of sound are Harmonics and Envelope. So far everything that we have discussed about sound, has been using a sine wave. Sine waves are pure tones of a single frequency. When you are engineering sound, you are almost never working with just one tone or frequency. Especially if you are in the music industry.

Harmonics

Harmonic content is what makes a sound unique and remember able. If there were no harmonics everything would sound the same, even peoples voices. But fortunately for us when notes are played or we speak, other frequencies are present along with the fundamental pitch. These other frequencies are called partials, and partials that are higher then the fundamental pitch are overtones. Any overtone that is multiple of a whole number of the fundamental frequency is called a harmonic. For example The note A has a frequency of 440 Hz. If we multiply this frequency by 2, we get 880 Hz. The 1st harmonic of this A is 440 Hz because if we multiply 440 by 1 we get 440. 880 Hz is the 2nd harmonic and 1320 Hz is the 3rd.

Our ears here these frequencies that are multiples of whole numbers and they see them as being related. This is called a Musical Octave and 880 Hz is 1 octave above 440Hz. If we go up another octave, its now 1760 Hz and the 3rd octave is 3520 Hz. The cool thing is that each instrument produces different partials as each note is played and the Harmonics Balance is called Timber. This is what makes an A note of a trumpet sound different from the same A on a french horn.

Envelope

The last thing on our list is the sound envelope. This is the start, middle, and end of a sound. This also helps us to identify what is making the sound along with timber. The start, middle, and end, can also be considered the Attack, Sustain, and Decay. Attack is how a sound builds up and Sustain is how long that sound last. Decay is how fast the sound disappears after it ends. Some instruments have a very fast attack and short sustain like the hit of a drum. Others will be slower and longer like a soft long note of a piano. All of this is to help us to distinguish one sound from another and it will be important for us to remember this as we start mixing these sounds together.